Metastable or transient materials often have unusual physicochemical properties, and many well-performing materials are in a particular metastable state. For example, during steel processing, an austenite is transformed into a metastable martensite through quenching, which greatly improves usability. The structures and properties of metastable materials have always been one of research hotspots, involving various research fields such as materials science, physics, chemistry, biology, energy, pharmacy, food and the environment. At present, the most simple and straightforward way to realize the metastable state of materials is heat treatment. Therefore, thermal analysis, especially fast thermal analysis, has become one of the most effective and reliable means for studying metastable materials.
In recent years, Professor Christoph Schick et al. have used a commercial thin film vacuum sensor (vacuum thermal conductivity gauge, TCG-3880, Xensor Integration, NL) to build the first fast scanning calorimeter (FSC) (Patent No.: US20100046573A1), and the controllable heating/cooling rate of the FSC is 1-10,000 K/s, or even higher. The specific approach is to load a sample of a nanogram to microgram level on the thin film sensor and significantly reduce the sample and additional heat capacity, so as to increase the heating/cooling rate. The method has been used to successfully study the melting-recrystallization-remelting process of many polymers, such as poly(dimethyl phthalate), polypropylene, polyamide blends and isotactic polystyrene. Since such a heating/cooling rate is sufficient to suppress the structural transformation of certain materials, fast scanning calorimetry can be used to study the thermodynamic properties of some metastable materials and also obtain the metastable state of the materials through fast heat treatment. However, the information provided by fast scanning calorimetry is limited and cannot meet the requirement for studying the structures and properties of metastable materials. Therefore, there is a need to develop a technical means which can be used to conduct fast thermal analysis on a sample to obtain the thermal properties of the sample, and at the same time to be integrated with microscopic structure characterization techniques to obtain the structure information of the sample in the metastable state.
There are two difficulties, though, to realize the above technical means. First, the available operation space of most microscopic structure characterization equipment is small, and the available FSC performs temperature control by immersing a vacuum tube in a Dewar flask and in-situ integration with other equipment cannot be achieved; for structure characterization of a metastable material prepared by the FSC, the sample can only be taken out and put into another equipment, and the internal structure of the sample may have changed during this process. Second, since the additional heat capacity of the sample and sensor adopted by the fast scanning calorimeter is small, even low-power incident light can significantly affect the temperature of the sample; however, the available FSC uses power compensation to control the temperature of the sample, and when the incident light used for structure characterization has an effect on the temperature of the sample that exceeds a power compensation limit, the temperature of the sample will be out of control, which may cause the structure of the sample to change.